Process for the deposition of copper-tin layers in the absence of current



United States Patent Int. Cl. C23c 3/00; c094 5/00 US. 01. 106-1 6 Claims ABSTRACT OF THE DISCLOSURE A process and solution for currentless deposition of copper-tin layers on iron and steel surfaces comprising immersing the surfaces in an aqueous solution at temperatures from 10 to 40 C. for approximately 0.5 to 5 minutes, removing the solution and rinsing the surfaces with water, the solution containing copper and tin ions calculated as CuSO -5H O to SnSO in Weight proportions of 0.2:1 to 0.5 :1, said copper being present in an amount of 1 to 20 grams per liter, 0.01 to 0.15% by weight of a compound of certain polyaminopolycarboxylic acids and their derivatives and more than 30 and up to 120 grams per liter of concentrated sulphuric acid.

This application is a continuation-in-part of our copending application Ser. No. 476,990, filed August 3, 1965.

The subject of our above named copending application is a process for the currentless deposition of copper-tin layers on iron and steel surfaces characterized by a treatment of the metal surfaces with an acid or neutral solution containing the sulfates of copper and bivalent tin in weight proportions of CuSO -5H O to SnSO4 of 1.8:1 to 1:2 and furthermore 0.01 to 0.15 weight percent of polyaminopolycarboxylic acid. In a preferred embodiment, the solutions contain 0.5-30 g./l. (grams per liter) concentrated sulfuric acid.

The instant invention has as its object an improvement of the process described whereby particularly glossy, well-adhering and light-colored coatings are obtained.

The novel process according to this invention is characterized by a solution which contains more than 30 and up to 120 g./l. concentrated sulfuric acid and proportions of copper to tin, calculated as CuSO -5H O to SnSO of 0.2:1 to 0.5:1.

It is required that the solutions contain the metals in the form of their sulfates because other ions, such as chlorides and nitrates, interfere with the metal deposition.

The concentration of the copper sulfate, calculated as CuSO -SH O, opportunely is held between 1 and 20 g./l., and preferably between 1 and 10 g./l. The concentration of the tin(II)-sulfate follows from the CuzSn proportions named above. Variations of these proportions infiuence the color of the copper-tin layers which vary from a light bronze to brass. Increases in the tin component lead to lighter colors.

The addition of polyaminopolycarboxylic acid to the copper-tin sulfate solutions is made in amounts of 0.01 to 0.15 weight percent and preferably is between 0.05 and 0.15 percent. Suitable acids of the kind are ethylenediaminotetraacetic acid (EDTA) and such other acids which resemble the latter in their properties, such as diethylenetriaminopentaacetic acid, N (2 hydroxycyclohexyl)ethylenediaminotriacetic acid, ethyleneglycol bis 3,454,407 Patented July 8, 1969 "ice (beta-aminoethylether)tetraacetic acid. These acids also can be employed in the form of their salts.

The solutions can be controlled by determination of their copper content. In order not to prolong the plating times unduly, it has been found advantageous to replenish the solution after it has attained approximately /3 of its original copper content. This replenishment can be carried out by adding the proportionate mixture of the solid components. The composition of this mixture opportunely is chosen so that the components are in the same proportions as originally present. This procedure can be repeated several times because the activity of such a solution is largely independent of the increasing iron concentration therein. Even iron concentrations of more than 30 g./1. do not interfere with the plating process, and this is a further great'advantage of the process according to the invention. Further addition of acids generally is not required for the replenishment of the solution.

The aqueous solutions can be employed at temperatures between 10 and 40 C. At room temperatures, 30 seconds to 5 minutes are required to deposit a welladhering layer of 1 to 3p thickness. The time depends upon the temperature and on the concentration of the solution. Therefore, the use of overly low temperatures or undue depletion of the solution is not recommended.

It has been found quite advantageous to add to the solutions small quantities of acid-resistant wetting agents, preferably nonionic ones. This eliminates the need for pre-cleaning of the metal surfaces when they are slightly soiled, while on the other hand final traces of, e.g., fats or greases remaining after pre-cleaning are removed thereby. The addition of such wetting agents in quantities of 0.1 to 3 g./l. has been found particularly advantageous.

When the metal surfaces are greatly soiled, the customary cleansing procedures with alkaline, acidic or neutral cleansers or with emulsion-type cleansers, is required prior to the deposition of the copper-tin layers.

After the deposition of the desired layers, the metal surfaces are rinsed with water to remove adhering solution, whereby it does not matter Whether rinsing is carried out with hot or cold water.

The copper-tin deposits according to the invention impart a decorative coloration and good properties upon cold shaping to the metal surfaces. They also are eminently suited as tie layers for the adhesion of rubber to metal.

The invention now will be further explained by the following examples. However, it should be understood that these are given merely by way of illustration, andnot of limitation, and that numerous changes may be made in the details without departing from the spirit and scope of the invention as hereinafter claimed.

EXAMPLE 1 An aqueous solution Was produced composed of the following ingredients:

G./l. 1. CuSO -5H O 4.5 2. SnSO 19.5 3. EDTA 1.45 4. Wetting agent (nonylphenol-i-S-ethylene oxide) 1 5. H (conc.)

After the solution had been depleted to approximately two-thirds of its original copper content, the concentration was restored by adding a mixture of powders of the following composition in weight percent using the numbers as listed above:

EXAMPLE 2 An aqueous 3 weight percent solution of a solid compound was prepared having the following composition:

Percent wt.

CUSO4'1H2O SnSO 58.1 Sodium salt of EDTA 4.7 Wetting agent (dodecylphenol+12-ethylene oxide)- 1 NaHSO 21.4

EXAMPLE 3 Well-adhering copper-tin layers were applied to wire and steel surfaces with aqueous solutions as named below within 0.5 to 5 minutes at temperatures ranging from 10 to 40 C. The layers ranged from 1 to 5y. in thickness.

G./l. CuSO -H O 6.5 SnSO 14.5 EDTA 1.0 H SO (d.=1.84) 40.0

The layer obtained had a light bronze hue and high gloss or sheen.

G./l. CUSO45H2O 5.5 SnSO 17.2 Diethylenetriaminepentaacetic acid 1.3 Wetting agent (octylphenol-i-9-ethylene oxide) 0.5 H SO (d.=1.84) 50.0

The copper-tin layer obtained had high gloss and a pleasant brass color.

CHSO4'5H2O 7.0 SnSO 17.5

N (2 hydroxycyclohexyl) ethylenediaminotriacetic acid 1.35 Wetting agent (alkylbenzenesulfonate) 0.3 H SO (d.=1.84) 60.0

4 The copper-tin layer thus produced had a light bronze color and high sheen.

G./l. CuSO 'SHQO 5.0 SnSO 16.8 Ethyleneglycol-bis (beta-aminoethylether) tetraacetic acid 1.25 H (d.=1.84) 80.0

A high-gloss brass-colored layer was obtained.

G./l. CuSO -5H O 4.0 SnSO 16.0 Beta,beta'-diaminodiethylethertetraacetic acid 1.3 Wetting agent (dodecyldiphenyloxydisulfonate) 0.5 H 80 (d.=1.84) 55.0

A light brass color was obtained, the copper-tin layer having high gloss.

G./l. CuSO -5H O 4.5 SnSO 20.0 EDTA 1.0 H 80 (d.=1.84) 120.0 Wetting agent (alkylbenzenesulfonate) 0.5

The high-gloss layer had a light bronze color.

All solutions could be replenished with solid mixtures of copper sulfate, tin sulfate and polyaminopolycarboxylic acids in the proportions given for each solution.

We claim as our invention:

1. A process for the currentless deposition of coppertin layers on iron and steel surfaces which comprises covering said surfaces with an aqueous solution at temperatures ranging substantially from 10 to 40 C. for approximately 0.5 to 5 minutes; removing said solution; and rinsing the surfaces with water; said solution containing copper and tin ions, calculated as CuSO -5H O to SnSO in weight proportions of 0.2:1 to 0.5 1, said copper being present at 1 to 20 grams per liter; 0.01 to 0.15 weight percent of a compound selected from the group consisting of ethylenediaminetetraacetic acid, diethylenetriaminopentaacetic acid, N-(Z-hydroxycyclohexyl)ethylenediaminotriacetic acid, ethyleneglycol bis(beta-aminoethylether)tetraacetic acid and beta,beta-diaminodiethyltetraacetic acid; and more than 30 and up to grams per liter of concentrated sulfuric acid.

2. The process as defined in claim 1, wherein said solution further contains 0.1 to 3 grams per liter of an acidresistant wetting agent.

3. The process as defined in claim 2, wherein said wetting agent is nonionic.

4. A plating solution for the currentless deposition of copper-tin layers on iron and steel surfaces comprising aqueous solutions of copper and tin ions, calculated as CuSO -5H O to SnSO in weight proportions of 0.2:1 to 0.5:1, said copper being present at 1 to 20 grams per liter; 0.01 to 0.15 weight percent of a compound selected from the group consisting of ethylenediaminotetraacetic acid, diethylenetriaminopentaacetic acid, N-(Z-hydroxycyclohexyl)ethylenediaminotriacetic acid, ethyleneglycolbis(beta-aminoethylether)tetraacetic acid, and beta,betadiaminoethyltetraacetic acid; and more than 30 and up to 120 grams per liter concentrated sulfuric acid.

5. The plating solution as defined in claim 4, wherein the same also contains 0.1 to 3 grams per liter of an acid-resistant wetting agent.

6. The plating solution as defined in claim 5, wherein said wetting agent is nonionic.

(References on following page) References Cited UNITED STATES PATENTS 6 OTHER REFERENCES Narcus: The Role of Chelating Agents in the Plating 4/1966 M00re 106 1 Industry, Metal Finishing, March 1952, pp. 54-62 relied 10/1967 Gardner 106-1 5 FOREIGN PATENTS JULIUS FROME, Primary Examiner.

2/1963 Canada. L. HAYES, Assistant Examiner. 11/1963 Canada.

5/1966 Canada. 6/1964 France. 0

Disclaimer 3,454,407.-Fm'te Mb'ller, Bensberg-Frankenforst, Heinz Groschopp, Dusseldorf-Holthausen, and Rudolf Wagenknecht, Cologne-Lindenthal, Germany. PROCESS FOR THE DEPOSITION OF COPPER-TIN LAYERS IN THE ABSENCE OF CURRENT. Patent dated July 8, 1969. Disclaimer filed Mar. 3, 1969, by the assignee, Gerhard Collardz'n G.m.b.H. Hereby disclaims the terminal portion of the term of the patent subsequent to Mar. 11, 1986.

[Ofli'oial Gazette Septembev' 30, 1.969.] 

